US3961364A - Color television camera - Google Patents

Color television camera Download PDF

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Publication number
US3961364A
US3961364A US05/527,267 US52726774A US3961364A US 3961364 A US3961364 A US 3961364A US 52726774 A US52726774 A US 52726774A US 3961364 A US3961364 A US 3961364A
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Prior art keywords
electrode
signal
color
elements
electrode segments
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US05/527,267
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English (en)
Inventor
Hiromichi Tanaka
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Panasonic Holdings Corp
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Matsushita Electric Industrial Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y10/00—Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J31/00—Cathode ray tubes; Electron beam tubes
    • H01J31/08—Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
    • H01J31/26—Image pick-up tubes having an input of visible light and electric output
    • H01J31/46—Tubes in which electrical output represents both intensity and colour of image
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N9/00—Details of colour television systems
    • H04N9/01—Circuitry for demodulating colour component signals modulated spatially by colour striped filters by phase separation

Definitions

  • the present invention relates to color television cameras and especially to the type employing a single pickup tube for producing a color video signal.
  • Apparatus of the type employing a single pickup tube for producing a color video signal are shown, for example, in U.S. Pat. Nos. 2,733,291 and 3,647,943, in which color component lights are spatially modulated at two different frequencies or at a single frequency provided by a striped color filter having stripes arranged in a predetermined angular direction with respect to the direction of the line scanning, and the output signals derived by the line scanning are passed through a plurality of bandpass filters or a comb-filter to separate color component signals, while on the other hand the third color component signal is derived from the unmodulated signals.
  • the conventional apparatus of this type have certain disadvantages, such as, the production of shading due to the difference in output waveform between the modulated signals and the unmodulated signal (including the A.C. components), and the instability of white balance due to the dark current.
  • a disadvantage of this apparatus is that since each of the electrode segments of the signal electrode must be divided at the recurrence frequency of one half the recurrence frequency of the striped color filter, the length of the dividing slot tends to be longer thus giving rise to a difficult problem of interelectrode stray capacitance and hence the same difficult problems of crosstalk, etc. as in the previously mentioned conventional apparatus.
  • Another disadvantage is that the spurious components produced at the dividing slot separating the electrode segments from each other interferes with the modulation frequency band of the chrominance signal or the low frequency signals.
  • the present invention comprises a color television camera of the type employing a single photoconductive type pickup tube having a signal electrode consisting of a plurality of transparent electrode segments, a striped color filter and a photoconductive surface, wherein a color separated image is formed on the photoconductive surface, at least one of the electrode segments constituting the signal electrode consists of a plurality of electrode elements each having a width greater than the recurrence cycle of the respective filter-element sets of the striped color filter, each of the electrode elements is provided with a plurality of beam current interrupting portions arranged at predetermined intervals smaller than the recurrence cycle of the filter element sets, whereby the spurious components produced at the dividing slot separating the plurality of electrode segments and the beam current interrupting portions in response to the line scanning are outside the frequency bands of the luminance signal and the modulated chrominance signal.
  • the sum signal of the output signals derived from the electrode segments is passed through a low-pass filter and a band-pass filter, respectively, to provide the luminance signal and the modulated chrominance signal from which the spurious components have been eliminated, and the reference signal required for synchronously detecting the modulated chrominance signal to produce color difference signals is provided by multiplying integral times an index signal derived from the output of at least one of the electrode segments.
  • the signal electrode consists of a plurality of electrode segments divided in such a manner that the resulting electrode elements are arranged at predetermined intervals of integral multiple of the recurrence cycle of the filter-element sets in the striped color filter, and each of the electrode elements is provided with a plurality of beam current interrupting slits arranged at the same intervals as the width of the filter elements.
  • the index signal is derived by producing the difference between the outputs derived from the electrode segments.
  • the signal electrode structure comprises a first electrode whose electrode elements are arranged at predetermined intervals of integral multiple of the recurrence cycle of the filter element sets, and a second electrode consists of a plurality of electrode elements each covering a plurality of the filter elements and provided with a plurality of beam current interrupting portions which are arranged at the same intervals as the width of the filter elements.
  • the composite signal of the output signals derived from the electrodes is passed through filters to provide the luminance signal and the modulated chrominance signal, and an index signal is derived from the first electrode.
  • a feature of this embodiment is that the phase of the index signal is not changed with the incident color component lights.
  • the apparatus according to the present invention has among its great advantages the fact that it is capable of reducing the number of separate electrode segments of the signal electrode with the result that the processing of the signal electrode is made easier, and the interelectrode stray capacitance is reduced thus making it possible to derive a relatively stable optical index.
  • Another advantage of the apparatus of the invention is that it is capable of eliminating the effects of the spurious components produced by the beam current interrupting portions including the dividing slot.
  • Still another advantage is that contrary to the apparatus as disclosed in U.S. Pat. No. 3,688,020 in which the index signal is produced electrically, the apparatus of this invention is realized with a relatively simple construction, and there is no line crawl generation which would otherwise be produced on the reproduced picture due to the phase reversal of the index signal caused between the succeeding lines in the operation within the relatively small range of the target current.
  • FIG. 1 is a schematic diagram showing an exemplary form of a pickup tube used in a color television camera according to the present invention
  • FIG. 2 is a schematic diagram showing the color filter used in the pickup tube of FIG. 1;
  • FIG. 3 is a block diagram showing the principal part of an embodiment of the color television camera of the invention shown schematically in FIG. 1;
  • FIGS. 4a through 4f are waveform diagrams which are useful in explaining the operation of the embodiment shown in FIG. 3;
  • FIG. 5 is a schematic diagram showing another form of the transparent electrode structure used in the pickup tube of the invention.
  • FIG. 6 is a block diagram showing the principal part of another embodiment of the color television camera according to the invention.
  • FIGS. 7g and 7h are waveform diagrams which are useful in explaining the operation of the embodiment shown in FIG. 6;
  • FIG. 8 is a block diagram showing the principal part of still another embodiment of the color television camera of the invention.
  • FIG. 1 there is illustrated an exemplary form of a pickup tube used in a single tube color television camera in accordance with the present invention.
  • numeral 1 designates an object to be televised
  • 2 a pickup tube
  • 3 a lens for focusing an optical image of the object to be televised on a photoconductive surface 8 of the pickup tube 2
  • 4 the face plate of the pickup tube 2
  • 5 a striped color filter
  • 6 an insulating layer
  • 7 a transparent electrode.
  • the striped color filter 5 comprises a plurality of recurrently arranged sets of filter elements F R , F B and F G for respectively passing red, blue and green component lights.
  • the transparent electrode 7 is constructed as shown in FIG.
  • the electrode segment 71 and 72 are divided by a dividing slot 11 at intervals of two times the recurrence cycle of the filter-element sets to form electrode elements 12 and 13.
  • Each of the electrode elements is provided with a plurality of electrode-removed portions 14 for interrupting beam current each having the same width as the dividing slot 11 in the electrode segments.
  • the signals respectively generated at output terminals 9 and 10 of the electrode segments 71 and 72 by the line scanning are respectively applied to preamplifiers 101 and 102 whose output signals are respectively shown in FIGS. 4a and 4b.
  • numeral 41 indicates those portions where there are no signal components due to the dividing slot 11 and the removed portions 14 of the transparent electrode 7 (the portions are hereinafter referred as spurious components), and the hatched portions designated by numeral 42 are crosstalk components due to the presence of the interelectrode stray capacitance.
  • These output signals are applied to an adder circuit 103 and a subtractor circuit 104 so that the output signals shown in FIGS.
  • the output signal d is applied to a limiter 106 through a band-pass filter 105 whose center frequency is the recurrence frequency of the electrode elements, so that the limiter 106 generates the index signal shown in FIG. 4e.
  • the output signal c of the adder circuit 103 is applied to a low-pass filter 108 and a band-pass filter 109 whose center frequency is the recurrence frequency of the striped color filter 5, so that the low-pass filter 108 and the band-pass filter 109 generate respectively a luminance signal and a modulated chrominance signal both of which include no spurious components.
  • the modulated chrominance signal is applied to synchronous detectors 110 and 111, so that the modulated chrominance signal is synchronously detected in accordance with the phase adjusted reference signal f shown in FIG.
  • An encoder 114 receives the luminance signal through a delay line 113 and the synchronously detected color difference signals and it generates an NTSC standard signal at its output terminal 115.
  • the dividing interval of the electrode segments is selected smaller than the recurrence cycle of the filter-element sets, it results in an increased interelectrode stray capacitance and hence it is difficult to provide the required index signal sufficiently by the effect of crosstalk.
  • the dividing interval of the electrode segments is selected greater than the recurrence cycle of the filter element sets, the spurious components generated at the dividing slot tend to interfere with the video signal with a resulting adverse effects.
  • the fundamental frequency of the spurious components generated at the electrode-removed portions 14 and the dividing slot 11 formed in the electrode elements 12 and 13 is three times as large as the modulation frequency of the chrominance signal and it is outside of the frequency bands of the luminance signal and the modulated chrominance signal, thus eliminating the occurrence of such adverse effects by taking off the spurious component with the low-pass filter 108 and band-pass filter 109.
  • FIG. 5 there is illustrated another form of the transparent electrode structure with which the video signal generating circuit shown in FIG. 3 can be used without any modification.
  • the portions corresponding to those of the structure of FIG. 3 are designated by the same reference numerals with a prime.
  • the electrode structure of FIG. 5 differs from the structure of the transparent electrode 7 shown in FIG. 3 in that while electrode segments 71' and 72' are divided at the same intervals as in the electrode structure shown in FIG. 3, the interval between the respective removed portions 14' in the respective electrode element is selected as one half the recurrence cycle of the striped color filter-element sets.
  • the fundamental frequency of the spurious components is two times the modulation frequency of the chrominance signal, and therefore these spurious components may be removed through the band-pass filter 109 and the low-pass filter 108.
  • the electrode structure shown in FIG. 5 ensures a high degree of light utilization and hence an improved sensitivity as compared with the electrode structure shown in FIG. 3.
  • the width of the electrode elements need not always be selected to be an integral multiple of the recurrence cycle of the striped color filter-element sets, and it is only necessary that any selected width of the electrode elements satisfies a relationship so that the difference signal generated by multiplying the frequency of the index signal by integral times, which produced from the output signal of at least one of the electrode segments (i.e., the electrode segments 71' and 72') has the same frequency as the chrominance modulation frequency.
  • the width of the electrode elements may be selected about two and half times the recurrence cycle of the filter-element sets of the striped color filter. In this case, it is necessary that the N-fold frequency multiplier 107 consists of a frequency quintupler which multiplies by five times the frequency of the generated index signal to generate the required reference signal.
  • FIG. 6 illustrates another embodiment of the color television camera according to the present invention.
  • the transparent electrode consists of electrode segments 15 and 16.
  • each of electrode elements 17 is associated with a given filter element which passes a specified color (in this embodiment, a filter element F G which passes the G component), and the interval between the electrode elements 17 is four times the recurrence cycle of the filter-element sets
  • the electrode segment 16 is provided with a plurality of elements 18 each covering the plurality of the filter elements between the elements 17, and the elements 18 are provided with electrode-removed portions 19 arranged at the intervals corresponding to the width of the striped color filter elements.
  • the outputs generated from the electrode segments 15 and 16 by the line scanning are respectively passed through preamplifiers 201 and 202, and they are then applied to an adder circuit 203.
  • the output waveforms of the preamplifiers 201 and 202 are respectively shown in FIGS. 7g and 7h, and in these waveforms numeral 43 indicates the spurious components and numeral 44 designates the components due to crosstalk between the electrodes.
  • the reference signal is applied, after phase adjustment, to a synchronous detector 209 for generating a color difference signal (R - Y) and to a synchronous detector 210 for generating a color difference signal (B - Y) through a phase shifter 211.
  • the output of the adder circuit 203 is applied, in the same manner as in the embodiment shown in FIG. 3, to a low-pass filter 207 and a band-pass filter 208, so that the low-pass filter 207 generates as its output the luminance signal, and the band-pass filter 208 generates as its output the modulated chrominance signal which is subjected to synchronous detection in the synchronous detectors 209 and 210 to generate the color difference signals.
  • An encoder 213 receives the luminance signal Y through a delay line 212 and the color difference signals (R - Y) and (B - Y) so that these input signals are matrixed to generate an NTSC standard signal at an output terminal 214.
  • the spurious components 43 are removed by the low-pass filter 207 and the band-pass filter 208.
  • a feature of the second embodiment is that the phase of the index signal is not changed by changes in the color components in the incident light, since each electrode element 17 is associated with the filter element (F G ) which passes a specified color component (green incident light in this case).
  • F G filter element
  • the signal-to-noise ratio of the index signal is not satisfactory.
  • a pair of electrodes for providing an index signal may be arranged as shown in FIG. 8.
  • the electrode structure consists of an electrode segment 151 corresponding to the electrode segment 15 and having a plurality of electrode elements 171, an electrode segment 152 having each electrode element 172 arranged midway between the electrode elements 171 and associated with the same color component passing filter element (F G ) as that of the electrode elements 171, and an electrode segment 161 corresponding to the electrode segment 16 shown in FIG. 6.
  • the output signals of the electrode segments 151 and 152 are respectively passed through preamplifiers 301 and 302 and are then applied to a subtractor 303 which generates the difference between the signals to provide an index signal, and consequently it is possible to provide the index signal having a greater amplitude and thereby to provide an improved S/N ratio of the index signal.
  • the luminance signal and the chrominance signal are generated by adding the output signals derived from the three electrode segments in an adder 304 and then applying the output signal of the adder 304 to a low-pass filter 207 and a band-pass filter 208.
  • the remaining blocks of the video signal generating circuit are the same with the corresponding blocks in the embodiment of FIG. 6 and therefore they will not be described.
  • the transparent signal electrode is formed with slits to provide the required beam current interrupting portions in the electrode elements
  • the same results may be accomplished by depositing for example coatings of SiO 2 or photo resist on the surfaces of the electrode segments facing in the direction of movement of the beam.
  • the deposition of such beam current interrupting material is easier than the formation of slits in the hard transparent electrode.
  • the electrode segments are provided in the form of combs, it is of course possible to provide the required electrode segment by connecting a large number of electrode elements to a bus bar.
  • the beam current interrupting portions formed in the electrode segments are provided so that the spurious components are not in the same bands as the luminance signal and the chrominance signal, they need not be provided with such a high degree of accuracy as required for the dividing slot which must completely separate the electrode segments from each other to permit the production of index signals.
  • the desired results may be achieved even if the slit or slits in the electrode elements are partially short circuited. Consequently, as in the present invention, to reduce the number of the divided electrode segments in the signal electrode that usually requires a high degree of processing accuracy; that is, to reduce the length of the dividing slot has the effect of not only reducing the stray capacitances and hence crosstalk, but also ensuring an improved yield.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Nanotechnology (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Mathematical Physics (AREA)
  • Theoretical Computer Science (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Color Television Image Signal Generators (AREA)
  • Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
US05/527,267 1973-11-27 1974-11-26 Color television camera Expired - Lifetime US3961364A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP13388373A JPS5338138B2 (enrdf_load_html_response) 1973-11-27 1973-11-27
JA48-133883 1973-11-27

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US3961364A true US3961364A (en) 1976-06-01

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JP (1) JPS5338138B2 (enrdf_load_html_response)
CA (1) CA1008556A (enrdf_load_html_response)
DE (1) DE2455881C3 (enrdf_load_html_response)
GB (1) GB1486438A (enrdf_load_html_response)

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JPS59141971U (ja) * 1983-03-11 1984-09-21 三洋電機株式会社 食器洗浄機

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2843659A (en) * 1950-12-23 1958-07-15 Emi Ltd Color television apparatus
US3721752A (en) * 1970-12-24 1973-03-20 Sony Corp Image pickup tube

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2843659A (en) * 1950-12-23 1958-07-15 Emi Ltd Color television apparatus
US3721752A (en) * 1970-12-24 1973-03-20 Sony Corp Image pickup tube

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DE2455881C3 (de) 1980-01-17
DE2455881A1 (de) 1975-10-16
JPS5084136A (enrdf_load_html_response) 1975-07-07
GB1486438A (en) 1977-09-21
JPS5338138B2 (enrdf_load_html_response) 1978-10-13
CA1008556A (en) 1977-04-12
DE2455881B2 (de) 1979-05-23

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